Development and test of Venlo greenhouse roof cleaning machine

Mechanical equipment is still lacking to clean the roofs of domestic Venlo-type greenhouses. The Manual cleaning can be time-consuming and labor-intensive so far. The existing solutions are relied excessively on imported equipment, resulting in high costs and maintenance expenses that significantly increased production costs. In this study, an electric roof cleaning machine was designed to automatically clean and switch the roofs of the Venlo-type greenhouses. A walking drive device was designed to ensure the consistent driving of the cleaning machine wheels, while reducing the wheel slippage on the damp tracks. A single motor was combined with a reducer and universal joint for the power transmission, in order to ensure the synchronous rotation of all four wheels. The resistance faced by the cleaning machine during movement was analyzed and calculated to determine the torque and power requirements for driving the motor. A uniform winding device was designed for uneven cable or water pipe winding during operation. The important parameters of the winding wheel were determined to accommodate the sufficient cable or water pipe length for each cleaning task. The winding and unwinding process of the uniform winding device was analyzed to clarify the impact of changes in the winding radius on the winding speed. The initial stage control of unwinding and the end stage of winding were optimized to prevent the excessive stretching of the cable or water pipe, thus avoiding a reduction in their lifespan. Reliable brushing was realized on the greenhouse roof using the cleaning roller brush. There was a contact process between the bristles and the roof surface. The roller brush fully met the design requirements to wash the roof surface under the conditions of 15 mm bristle deformation and a cleaning machine travel speed of 0.25 m/s. The torque resistance experienced by the roller brush was calculated to obtain the motor power required for the driving rotation of the roller brush. Some installation of switching tracks and positioning markers was carried out for Venlo-type connected greenhouses, in order to ensure the smooth progress of the switching operation. The rational design was achieved in the automatic water supply system for the auxiliary switching platform and the switching control system. A safety redundant control system was designed using multiple sensor perceptions for the cleaning machine. The various motor operations were controlled in an orderly manner, in order to collect the processing signals, such as the edge, departure detection, coiling, and skylight opening signals. A prototype was fabricated to conduct the test greenhouse, followed by performance testing of the prototype. The test results indicated that the cleaning machine achieved the maximum operating speed of 0.265 m/s, with a stop margin of 28.4 mm. The average switching time was 22.84 s, and the average alignment error between the platform and the roof track was 1.6 mm. An experiment was conducted to evaluate the cleaning effectiveness of the machine using the transmittance rate of the film as an indicator. The results showed that the transmittance rate increased to 86% after cleaning under the conditions of a travel speed of 0.25 m/s, roller brush speed of 120 r/min, and water pump flow rate of 34 L/min using a film with an initial transmittance rate of 68%. Better cleaning performance was achieved during operation. The cleaning machine can fully meet the cleaning requirements of Venlo-type greenhouse roofs. It is of significant importance in the indoor temperature and light environment, as well as the higher fruit yield and quality.